Device for stacking tube sections for producing bags

ABSTRACT

Device for stacking tube sections ( 30 ) for producing bags, with a transporting facility ( 12 ), which supplies the tube sections to a stacking station ( 10 ), characterized in that the transporting facility ( 12 ) has an upper transport ( 14 ) and a lower transport ( 16 ) and that the lower transport ( 16 ) is formed in the region of the stacking station ( 10 ) by two endless conveyor belts ( 44 ), which revolve above the stacking station outside of the lateral edges of the tube sections ( 30 ) and are connected by at least two cross members ( 48, 50 ), which are disposed with uniform spacings, the spacings of which corresponding to the spacings between the leading edges of consecutively supplied tube sections ( 30 ).

[0001] The invention relates to a device for stacking tube sections forproducing bags, with a transporting facility, which supplies the tubesections to a stacking station.

[0002] For producing bags of paper or film, an endless tube isfrequently produced first and then divided into individual tubesections, each of which forms a bag. The individual tube sections, whichare transported continuously and consecutively with a transportingfacility, are then frequently, to begin with, collected in a stack. Onlyin a later operation are the ends of the tube sections closed and thebags optionally filled with their content.

[0003] For certain applications, bags are required, which havemultilayer walls, for example, a wall with a layer of paper and at leastone layer of film, which is impermeable to air. One example of such bagsis inflatable bags, which are used as supporting cushions for thetransport of goods.

[0004] Frequently, particularly in the case of multilayer bags that arerelatively long, it often proves to be difficult to stack the tubesections cleanly one above the other. When a freshly supplied tubesection is pushed or pulled during a stacking process over the uppermosttube section, which is already lying on the stack, the individual layersof material can easily slip out of place relative to one another and/orform folds, so that a clean stack and a satisfactorily furtherprocessing are not possible.

[0005] It is an object of the invention to provide a device, which makesclean stacking possible even in the case of tube sections of a flexible,slack or multilayer material.

[0006] Pursuant to the invention, this objective is accomplished owingto the fact that the transporting facility has an upper transport and alower transport and that the lower transport, in the region of thestacking station, is formed by two endless conveyor belts, which revolveabove the stacking station outside of the lateral edges of the tubesections, and by at least two cross members, which are disposed withuniform spacing, the spacing corresponding to the spacing of the leadingedges of the tube sections, which are supplied consecutively.

[0007] With the help of the transporting facility, the tube sections aresupplied above the stack, which is being formed. At the same time, theleading edge of a tube section is clamped between the upper transportand one of the cross members of the lower transport. When the stackingposition is reached, the cross member of the lower transport reaches theturn-around roller, at which the conveyor belt is turned around and,consequently, the clamping of the leading edge between the uppertransport and the lower transport is canceled, so that the tube sectiondrops onto the stack. While the next tube section with the subsequentcross member is being supplied, the turned-around cross member isreturned on the lower section of the conveyor belt. In so doing, itmoves on a path, which is also above the stack that is being formed. Thetrailing rear part of the newly supplied tube section, which is clampedonly at the front edge, is therefore kept away from the upper side ofthe stack by the returning cross member, so that it does not graze overthe stack and therefore cannot shift the tube sections present there.Only after the tube section, newly supplied, has been allowed to drop,has the lower cross member moved back so far, that it releases thetrailing edge of this tube section.

[0008] It is a further object of the invention to provide a method forstacking tube sections, especially tube sections of a multilayermaterial, for producing bags, for which the tube section is clamped withits leading edge between a cross member of a lower transport and anupper transport and supplied in a position above the stacking station,while a different cross member of the lower transport, which is returnedabove the stacking station to the upstream end of the transportingfacility, keeps the trailing, rear part of the tube section away fromthe, stack until the leading edge is released by the first cross memberand the tube section falls onto the stack.

[0009] Advantageous developments of the invention arise out of thedependent claims.

[0010] Preferably, the lower transport has precisely two cross members,which are disposed diametrically opposite to one another on the conveyorbelts.

[0011] Preferably, the lower transport extends somewhat beyond the uppertransport at the downstream end of the transporting facility, so thatthe released tube section can fall freely onto the stack.

[0012] The released tube section can be pressed down in the direction ofthe stack by one or more leaf springs, which are disposed in stationaryfashion in the upper transport, so that the depositing of the tubesection on the stack is accelerated.

[0013] The action of depositing the tube sections flush on the stack canbe aided by stops at the stacking table. Preferably, the stacking tableis formed by a conveyor, with which the stack can be transported away assoon as it has reached the desired height.

[0014] A severing device, in which the endless tube is divided intoindividual tube sections, preferably is disposed upstream from thetransporting facility above the stacking station. The transporting speedof the transporting facility above the depositing station preferably isgreater than the transporting speed, with which the tube is supplied tothe severing device. Since the tube sections, upon entering the stackingdevice, accordingly are accelerated, spaces are formed between theconsecutively supplied tube sections and provide sufficient time fordepositing the tube sections on the stack.

[0015] The lower transport must be synchronized with the tube sectionssupplied, so that each cross member arrives at the same time with theleading edge of a tube section supplied at the upstream end of thetransporting facility. Since the spaces, formed between the individualtube sections because of the acceleration depend on the differencebetween the transporting speeds, the distances between the leading edgesof consecutive tube sections can be adapted to the spacing of the crossmembers of the lower transport.

[0016] Particularly in the case of multilayer tube sections, thesevering device is constructed preferably as a tear-off head, with whichthe individual layers of material of the tube are torn off at previouslyformed perforation sites. Due to the acceleration of the tube sectionsupon entry into the transporting facility of the stacking device, thetensile stress, required to tear of the tube sections, can be producedat the same time.

[0017] Preferably, at the upstream end, the transporting facility of thestacking device has an inlet section, in which the vertical distancebetween the upper transport and the lower transport becomes narrower,until finally the leading edge of the tube section is clamped. Theclamping site preferably is defined by a clamping roller, which can beadjusted in the longitudinal direction so that it can be adapted fordifferent lengths of the tube sections.

[0018] In the following, an example of the invention is explained ingreater detail by means of the drawing, in which

[0019]FIG. 1 shows a diagrammatic side view of a stacking device,

[0020]FIG. 2 shows a device of FIG. 1 in plan view and

[0021]FIGS. 3 and 4 show side views of a device, similar to that of FIG.1, however for different phases of the stacking process.

[0022] The stacking device, shown in FIG. 1, has a stacking station 10,above which a transporting facility 12 with an upper transport 14 and alower transport 16 is disposed.

[0023] An endless, multilayer tube 18 is supplied from the right in FIG.1 with the help of upper and lower conveyor belts 20, 22. The walls ofthe tube 18 consist of several layers of material, which, to begin with,are perforated at positions preferably offset somewhat with respect toone another in the longitudinal direction.

[0024] Behind the conveyor belts 20, 22, the tube 18 enters a tear-offhead 24, which is also formed by the upper and lower conveyor belts 26,28. The transporting speed of the tear-off head 24 is greater at leaston a phase level than the transporting speed of the conveyor belts 20,22, so that a tensile stress is produced in the tube 18. When theaforementioned perforation site reaches the space between the downstreamend of the conveyor belts 20, 22 and the upstream end of the tear-offhead 24, this tensile stress causes the tube section 30 to be torn fromthe endless tube 18.

[0025] At this instant, the leading edge of the tube section 30 hasalready entered the inlet section 32 of the transporting facility 12.The inlet section is formed by several parallel upper and lower conveyorbelts 34, 36, the transporting speed of which is identical with that ofthe tear-off head 24. The vertical distance between the upper conveyorbelts 34 and the lower conveyor belt 36 gradually decreases in thetransporting direction, so that it becomes possible to introduce theleading edge of the tube section 30 reliably. A clamping roller 38directs the lower half of the upper conveyor belts 34 somewhat in thedownward direction, so that the leading edge of the tube section 30 isclamped at the instant, at which the trailing edge of the endless tubeis torn off. The clamping roller 38 can be adjusted to adapt to thelength of the tube section 30.

[0026] The transporting path, formed by the inlet section 32, isinclined slightly upwards, so that the tube sections, during the furthertransport, reach a certain height above the stacking station 10. In theregion above the stacking station, the upper transport 14 is formed byseveral parallel conveyor belts 14, which extend in the horizontaldirection and share a turnaround roller 42 with the conveyor belts 34.The lower transport 16 is formed here by two conveyor belts 44, whichrun over two turn-around rollers 46 and, as can be seen more clearly inFIG. 2, lie outside of the lateral edges of the tube section 30. Theconveyor belts 44 are connected by cross members 48, 50 only at twoplaces and are synchronized by positive driving mechanisms, such ascogged belts. The cross members 48, 50 are disposed at the conveyorbelts 44 in diametrically opposite positions, so that they have equalspacing to one another on both paths along the conveyor belts 44 andconsequently reach the turn-around roller at the same time. In thestate, shown in FIG. 1, the leading edge of a tube section 30 is clampedby the conveyor belts 40 of the upper transport and held by the crossmember 48. The trailing, rear end of this tube section 30 rests on theother cross member 50, which returns on the lower half of the conveyorbelts 44 to the upstream turn-around roller 46. In this way, the tubesection 30 is kept away from an already formed stack 52 of tubesections, which rests in the stacking station 10 on a stacking table 54,which is constructed as a conveyor.

[0027] In FIG. 2, the stacking device is shown in plan view. To improvethe clarity, only the upper conveyor belts 20, 36 and 34 with theirrespective turn-around rollers are shown on the supplying side. In thedownstream region, however, the conveyor belts 44 of the lower transportare also drawn. It can be seen that the distance between these conveyorbelts 44 is greater than the width of the tube section 30 supplied, sothat the tube section, when released, falls between these conveyor belts44 and can reach the stack 52. The depositing of the tube section 30 onthe stack 52 is supported by leaf springs 56, which extend in thelongitudinal direction between the conveyor belts 40 of the uppertransport and are fastened at a stationary support 58, so that, withtheir free ends, they press on the tube section 30 in the region of theleading edge.

[0028]FIG. 3 shows the stacking device in a state, which chronologicallyis a little later than the state shown in FIG. 1. The upper cross member48 has just passed the downstream end of the upper transport 14 here, sothat the tube section 30, supported by the action of the leaf springs56, falls on the stack 52. The tube section still has a certain velocitycomponent in the direction of motion, which, however, in the case of thepreferred transporting speed of the transporting facility 12, is onlyslight (preferably less than 60 meters per minute), so that the tubesection comes to rest in position on the stack 52. If necessary thealignment on the stack is supported by a stop 60, which is mountedsecurely on the stacking table 54.

[0029] In FIG. 3, the rear edge of the tube section 30 just passesthrough the lower cross member 50 and, accordingly, is also dropped onthe stack 52.

[0030]FIG. 4 shows the state at a sill later time. The cross member 48has just been turned around here at the turn-around roller 46 and nowreturns on the underside of the lower transport. At the same time, theother cross member 50 has reached the corresponding position on theupper side of the lower transport where, together with the conveyorbelts 40 of the upper transport, it now takes hold of leading edge ofthe next tube section 30, which is supplied at the proper time by theinlet section 32. This tube section is then pulled further forward. Whenits trailing edge has passed by the rear turn-around roller 46 of thelower transport and fallen down, it is caught by the returning crossmember 48, so that it does not come into contact with the stack 52.Finally, the condition, shown in. FIG. 1 is reached once again, so thata new cycle can commence.

[0031] When the stack 52 has reached the desired height, the conveyorbelt, which forms the stacking table 54, is started up, so that thestack is transported away and a new stack can be formed in the stackingsection 10.

[0032] For the stacking device described, the length of the tube section30 can be varied within certain limits, since the distance between thecross member 48 and 50 must agree with the distances between the leadingedges of consecutive tube sections and not with the precise length ofthe tube sections. Accordingly, a shorter length of the tube sectionscan be compensate for by appropriately larger spacings.

[0033] In a modified embodiment the lower transport 16 may also havemore than two cross members, distributed uniformly over the length ofthe conveyor belts 44. In this case, the tube sections 30 aretransported over a greater length, before they are deposited on thestack. The cross members 48, 50 may then be fastened detachably at theconveyor belts 44, so that their number can be varied.

[0034] Since it is at least largely avoided with the device describedthat a new tube section, supplied to the stack, drags over the uppersurface of the already formed stack a clean stack becomes possibleespecially in the case of sensitive, multilayer tube sections.

What is claimed is:
 1. Device for stacking tube sections for producingbags, comprising a transporting facility which supplies the tubesections to a stacking station the transporting facility including: anupper transport, a lower transport formed in a region of the stackingstation by two endless conveyor belts, which revolve above the stackingstation outside of lateral edges of the tube sections, and at least twocross members which connect the two endless conveyor belts and which aredisposed with uniform spacings corresponding to spacings between leadingedges of consecutively supplied tube sections.
 2. The device of claim 1,wherein downstream ends of the lower transport and the upper transportare offset relative to one another in a longitudinal direction thereof.3. The device of claim 1, wherein at least one leaf spring is disposedin the upper transport and presses the tube section provided downward ina direction of the stacking station.
 4. The device of claim 1, whereinthe transporting facility has an inlet section, in which a verticaldistance between the upper and lower conveyor belts decreases in atransporting direction.
 5. The device of claim 4, further comprising alength-adjustable clamping roller in the inlet section, which deflectsthe upper conveyor belt against the lower conveyor belt, in order totake hold of the leading edge of a tube section, which has beensupplied.
 6. The transporting facility of claim 1, further comprising asevering device upstream from the transporting facility, with which anendless tube is divided into tube sections.
 7. The device of claim 6,wherein the severing device has a tear-of head, which tears off the tubesections at pre-perforated places from an endless tube.
 8. The device ofclaim 6, wherein a transporting speed of the transporting facility isgreater than a speed with which the tube is supplied upstream to thesevering device.
 9. A method for stacking tube sections used forproducing bags, comprising the steps of: holding a tube section in atransporting facility with a leading edge thereof clamped between across member of a lower transport and an upper transport, and supplyingthe tube section to a position above a stacking station, while adifferent cross member of the lower transport, which is returning abovethe stacking station to an upstream end of the transporting facility,holds a trailing, rear end of the tube section away from the stack,until the leading edge is released by the first cross member and thetube section falls onto the stack.
 10. The device of claim 2, wherein atleast one leaf spring is disposed in the upper transport and presses thetube section provided downward in a direction of the stacking station.11. The device of claim 2, wherein the transporting facility has aninlet section, in which a vertical distance between the upper and lowerconveyor belts decreases in a transporting direction.
 12. The device ofclaim 3, wherein the transporting facility has an inlet section, inwhich a vertical distance between the upper and lower conveyor beltsdecreases in a transporting direction.
 13. The transporting facility ofclaim 2, further comprising a severing device upstream from thetransporting facility, with which an endless tube is divided into tubesections.
 14. The transporting facility of claim 3, further comprising asevering device upstream from the transporting facility, with which anendless tube is divided into tube sections.
 15. The transportingfacility of claim 4, further comprising a severing device upstream fromthe transporting facility, with which an endless tube is divided intotube sections.
 16. The transporting facility of claim 5, furthercomprising a severing device upstream from the transporting facility,with which an endless tube is divided into tube sections.
 17. The deviceof claim 7, wherein a transporting speed of the transporting facility isgreater than a speed, with which the tube is supplied upstream to thesevering device.